Chapter 4Chapter 4Electron ConfigurationsElectron Configurations

By Mr. EnglishBy Mr. English

Light as a waveLight as a wave

4.1 Objectives4.1 Objectives Describe wave in terms of frequency, speed, Describe wave in terms of frequency, speed,

wavelength and amplitudewavelength and amplitude List and explain the wave-like properties of List and explain the wave-like properties of

lightlight Identify the major regions of the Identify the major regions of the

electromagnetic spectrumelectromagnetic spectrum

Aspects of a waveAspects of a wave WavelengthWavelength

Typical units: nanometers (nm), meters (m)Typical units: nanometers (nm), meters (m) AmplitudeAmplitude

Typical units: volts/meter (this measurement is very Typical units: volts/meter (this measurement is very important to radio broadcasters. WHY?)important to radio broadcasters. WHY?)

Aspects of a moving waveAspects of a moving wave Frequency= number of wave cycles/ unit timeFrequency= number of wave cycles/ unit time

Typical units: cycles/sec, 1/sec, secTypical units: cycles/sec, 1/sec, sec-1-1, Hertz, Hz, Hertz, Hz All of the units above mean EXACTLY the same thingAll of the units above mean EXACTLY the same thing

Period= unit of time per wave cyclePeriod= unit of time per wave cycle Typical units: sec/cycle, sec, minutes, hoursTypical units: sec/cycle, sec, minutes, hours

Speed=distance traveled per unit timeSpeed=distance traveled per unit time Typical units: m/sec, cm/sec, miles/hour, (unit length)/(unit time)Typical units: m/sec, cm/sec, miles/hour, (unit length)/(unit time)

Properties of wavesProperties of waves

Waves can interfere constructively or Waves can interfere constructively or destructively with themselvesdestructively with themselves

They can be diffractedThey can be diffracted Waves of different frequencies bend at Waves of different frequencies bend at

different angles when they pass through a different angles when they pass through a series of parallel slitsseries of parallel slits

These are all properties of lightThese are all properties of light

What is a light waveWhat is a light wave

Vibrating magnetic field generates electricityVibrating magnetic field generates electricity Vibrating electric fields generate magnetismVibrating electric fields generate magnetism James Clerk Maxwell (mid 19James Clerk Maxwell (mid 19thth century) century)

calculated (from simple electrical experiments) calculated (from simple electrical experiments) the speed of a wave generated from a vibrating the speed of a wave generated from a vibrating electric and magnetic field: 3 x 10electric and magnetic field: 3 x 108 8 m/sm/s

Electromagnetic RadiationElectromagnetic Radiation

James Clerk Maxwell (mid 19James Clerk Maxwell (mid 19thth century) century) calculated (from simple electrical calculated (from simple electrical experiments) the speed of a wave experiments) the speed of a wave generated from a vibrating electric and generated from a vibrating electric and magnetic field: 3 x 10magnetic field: 3 x 108 8 m/sm/s

This was almost exactly the same as the This was almost exactly the same as the speed of light, which was known at the speed of light, which was known at the time.time.

What do you think Maxwell concluded?What do you think Maxwell concluded?

Electromagnetic spectrumElectromagnetic spectrum

The electromagnetic spectrum includes many The electromagnetic spectrum includes many types of energy unknown to Maxwell.types of energy unknown to Maxwell.

Electromagnetic spectrumElectromagnetic spectrum

What type of equipment (or natural What type of equipment (or natural senses) might be used to detect the senses) might be used to detect the amplitude of:amplitude of: ShortwaveShortwave MicrowaveMicrowave RadarRadar VisibleVisible UltravioletUltraviolet X-raysX-rays

C=C=

C = 3.00 x 10C = 3.00 x 1088 m/sec, the speed of EM m/sec, the speed of EM waveswaves

is lamda, the wavelengthis lamda, the wavelength is nu, the frequencyis nu, the frequency nm (nanometers)=10nm (nanometers)=10-9-9 meters meters What is the frequency of a red light, What is the frequency of a red light,

625nm?625nm? Solve by dimensional analysisSolve by dimensional analysis

What is the frequency of a red light, What is the frequency of a red light, 625nm?625nm?

First record all “given” information, or relevant info from First record all “given” information, or relevant info from other sourcesother sources

=625 nm, c=3.00 x 10=625 nm, c=3.00 x 1088 m/sec, 10 m/sec, 1099 nm = 1 m nm = 1 m Identify relevant formulas or relationships between Identify relevant formulas or relationships between

variables. variables. c=c==c/=c/ =c/=c/

The units must balance when you solveThe units must balance when you solve =c/=c/= = 3.00 x 103.00 x 1088mm 1_____1_____ 101099 nm nm = 4.80 x 10 = 4.80 x 101414 sec sec-1-1

sec 625 nm 1 msec 625 nm 1 m EvaluateEvaluate

Is the answer reasonable, is it written with correct significant Is the answer reasonable, is it written with correct significant digits, does it have a correct unit, is it the answer that was digits, does it have a correct unit, is it the answer that was requested in the problem.requested in the problem.

More problemsMore problems What is the wavelength of an x-ray with a What is the wavelength of an x-ray with a

frequency of 2.55 Hzfrequency of 2.55 Hz What is the frequency of a EM wave with a What is the frequency of a EM wave with a

length of 2.00 meters. What part of the EM length of 2.00 meters. What part of the EM spectrum is this in?spectrum is this in?

Determine the fastest rate you might be able to Determine the fastest rate you might be able to shake a handheld magnet. What frequency? shake a handheld magnet. What frequency? What wavelength is this? What part of the What wavelength is this? What part of the spectrum?spectrum?

How fast would you have to wag the magnet to How fast would you have to wag the magnet to generate visible light?generate visible light?

Light as a particleLight as a particle

4.2 Objectives4.2 Objectives Explain what is meant by quantum energyExplain what is meant by quantum energy Solve problems relating energy of radiation, Solve problems relating energy of radiation,

wavelength, and frequencywavelength, and frequency Discuss the dual nature of radiant energyDiscuss the dual nature of radiant energy

Hot!Hot!

Heated objects give off radiant energyHeated objects give off radiant energy

Study the picture below to answer Study the picture below to answer the questionsthe questions

What temperature is a star which emits with a maximum What temperature is a star which emits with a maximum intensity at 0.9 microns (900 nm)intensity at 0.9 microns (900 nm)

A candle flame burns at around 2000 K. Is its maximum A candle flame burns at around 2000 K. Is its maximum intensity above, below, or within the visible range of intensity above, below, or within the visible range of wavelengths?wavelengths?

Max Planck’s Theory (~1900)Max Planck’s Theory (~1900)

Planck proposed an explanation for the Planck proposed an explanation for the relationship between temperature and relationship between temperature and distribution of radiant wavelengths.distribution of radiant wavelengths.

His explanation required that energy is made up His explanation required that energy is made up of small indivisible parts he called “quanta”of small indivisible parts he called “quanta”

How is this similar to atomic theory?How is this similar to atomic theory? Plank’s equation: E=hPlank’s equation: E=h

Relates frequency to the size of the quantaRelates frequency to the size of the quanta h (Plank’s constant) = 6.6261 x 10h (Plank’s constant) = 6.6261 x 10-34 -34 JsecJsec

Can any color be used to charge a glowing object?

Red Yellow Green Blue

Photoelectric effectPhotoelectric effect

Photoelectric effect is similar to the glowing paint Photoelectric effect is similar to the glowing paint effecteffect

Electrons are ejected from the surface of certain Electrons are ejected from the surface of certain metals when light shines on the metalmetals when light shines on the metal

This can be used to generate an electric current, This can be used to generate an electric current, as in solar batteries.as in solar batteries.

But there is a minimum threshold frequency, But there is a minimum threshold frequency, below which the solar battery will not work at all, below which the solar battery will not work at all, REGARDLESS OF THE LIGHTS INTENSITYREGARDLESS OF THE LIGHTS INTENSITY

Einstein’s ExplanationEinstein’s Explanation Quanta can be thought of as “particles of light” Quanta can be thought of as “particles of light”

which Einstein called photonswhich Einstein called photons An individual photon either has enough energy An individual photon either has enough energy

to knock the electron off the surface of the metal, to knock the electron off the surface of the metal, or it doesn’tor it doesn’t

If the size of the individual photons are too small, If the size of the individual photons are too small, it doesn’t matter how many of them strike the it doesn’t matter how many of them strike the metal (how intense the light), the electrons will metal (how intense the light), the electrons will not be ejected.not be ejected.

E=hE=his the formula to determine if the light has is the formula to determine if the light has achieved the minimum threshold frequency to achieved the minimum threshold frequency to eject an electron.eject an electron.